Geo Ch 11
Match the pairs
A B Hanging wall is moving Type of Fault
Match (diagram 2)
A B Hanging wall moving Type of fault
Which of the following geographic provinces is the newest addition to the North American continent?
Coastal plain (CP consists of a blanket of sediments that have been deposited since the opening of the Atlantic)
Sort the following features and descriptions according to the two dip-slip faults shown.
Diagram 1 - hanging wall moves up relative to footwall - reverse fault Diagram 2 - hanging wall moves down relative to footwall - normal fault - caused by tensional forces (reverse + thrust faults caused by compressional forces; normal faults caused by extensional forces)
What is the orientation of a fold's hinge line with respect to the orientation of plunge?
Hinge line is in the direction of plunge (the direction of plunge is determined by the direction the hinge line descends into the Earth)
Which materials have been accreted to North America as terranes?
Iapetus Ocean Island Arc and sediments the Avalon Terrane a remnant of Africa (all of these landmasses stuck to North America and increased its size)
Rank the following events from OLDEST to YOUNGEST
Oldest - sediments deposited in a horizontal orientation the sediments are buried and lithified into sedimentary rock compressional forces cause the sed rocks to bend into an anticline youngest - processes of weathering and erosion expose the interior of the anticline
What sketch is the most accurate?
Sketch 5 (correctly outlines orientation of dipping beds, and the rock types that were discussed in text)
Which of the following orogenies helped to create the Appalachian Mountains?
Taconic Acadian Alleghanian (The Appalachians were built in three pulses over the course of nearly 200 million years)
Determine whether each geologic feature is being caused by tensional, compressional, or shear stresses.
Tensional = normal fault Shear = strike=slip fault Compressional = the three remaining
In a reverse fault, the hanging wall block moves up relative to the footwall block. T or F?
True
Which of the Appalachian Mountain belt Provinces are visible in the circled area of Figure 1?
Valley and Ridge
what produces plunging folds?
a combination of folding and tilting
Which of the following is the result of brittle deformation?
a reverse fault
What is the name of the process by which terranes are added to continents?
accretion (accretion occurs as a result of a subducting plate)
what do colors on geologic map represent
ages of rocks
Where do Andean-type mountain belts typically form?
along a subduction zone
Which of the following images best describes how a rock in the deep crust would be deformed as a result of shear stress?
because the rocks are at depth, the rocks will distort, but not fracture
Which tectonic boundary is associated with the addition of terranes to a continent?
convergent boundary (terranes are added to a continent through subduction)
Good example of a present-day, passive continental margin is the
east coast of North America
What does the term plunging fold mean?
fold tilted down into Earth
How did the North American Cordillera form?
from the collision of several island arcs with the west coast of North America
_____ is the principle that explains why materials uplift to a certain elevation.
isostasy
When a rock is under undue stress and fractures but there is no movement to either side of the fracture, the feature is called a _______. If, however, there is movement, it is called a ________.
joint fault
Drag appropriate labels.
left = anticline top = younger rock layer right = syncline bottom = older rock layer
What is the hinge line of a fold?
line of maximum inflection that layers wrap around (the hinge line is the location of greatest flexure in the rock layers)
__________ faults combine elements of strike-slip and dip-slip motions.
oblique-slip (oblique-slip movements will pull blocks apart as well as slide them past each other)
Imagine syncline eroded to a flat surface. How would the rock age change as you walked across that flat surface?
oldest on edges, youngest in middle
divergent plate boundary
tension
Which tectonic stress will result in a lengthening of the crust?
tension (tensional stress pulls things apart)
Why are terranes added to continental margins, rather than subducting under them?
terranes are too buoyant to subduct
How will the orientation of a plunging anticline's limbs change in the direction the fold is plunging?
the will close to a point (plunging anticlines close to a point, making an arrow in the direction of plunge)
Using the map in Figure 1, which province would the Rocky Mountains of the US be located?
young mountain belts (the uplift of the Rocky Mountains occurred approx. 60 million years ago)
What is a syncline?
a fold shaped like a right-side up U
What is an anticline?
a fold shaped like an upside down U
A graben is characterized by ________.
a hanging wall block that has moved down between two normal faults.
A thrust fault is best described as _______.
a low-angle, reverse fault
A terrane is ______
a mass of rock that formed elsewhere and was added to a continent (terranes are added to continents where subduction zones develop)
What is a terrane?
a slice of lithosphere that has been added to the margin of a continent during plate collision
geologic maps are used for
helping communities identify and prepare for natural disasters identification of mineral and water resources and ares where geothermal energy can be accessed
Where does most terrane accretion occur?
in association with a continental-oceanic subduction zone
Which of the following statements about terranes is most accurate?
margins of many continents have grown through accretion of terranes
Rank from shallowest to deepest
mountain arrows hammer
Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging?
nonplunging folds look like straight lines at surface, plunging folds look like wavy lines
What kind of fold is circled in Figure 1?
nonplunging syncline (nonplunging synclines will have limbs that point down toward the center of the fold
Large rifts or valleys, which can often have very large ________ faults, are created by tensional forces.
normal
Which fault will see the hanging wall move down relative to the footwall?
normal fault (normal faults are created by tension, which will pull the landscape apart)
Tensional forces normally cause which one of the following?
normal faults
Which of the following are mountain-building processes?
oceanic lithosphere subducting beneath continental and/or oceanic crust rifting of continental crust collision of two pieces of continental crust
Review statements and indicate which are correct.
one side of anticline dips more steely than the other at least one of the folds in this outcrop is asymmetrical
Which fold orientation is visible in figure 2?
overturned (limbs dipping same direction, different angles)
Which kind of fault is visible in Figure 1?
reverse fault (reverse faults are created when hanging wall moves up relative to footwall)
Which of the following is an example of how rocks will respond to compressional stress? (May be more than one correct answer)
reverse faulting folding (reverse faults occur when the landscape is shortened; folding occurs when the landscape is shortened)
Which of the following statements best describes the orientation of rock layers for a structural dome or structural basin?
rock layers wrap around a single point (domes and basins are round and will fold in all directions around a central point)
Imagine an anticline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface?
rocks would be youngest on the edges and oldest in the middle
If the Rocky Mountains were eroded, what would happen to the roots of the mountains?
roots would rebound upward (crust will uplift as weight is removed, which will also make the roots move upward)
Which of the following rocks are characteristic of compressional mountain building?
schist (metamorphic schist forms in high-pressure environments such as subduction zones)
transform plate boundary
shear
A(n) _____ fault has little or no vertical movements of the two blocks.
strike slip
which of the following best describes the orientation of the fold in figure 1?
symmetrical
A trough, or downward fold, called a(n) ________ is formed when a rock is deformed through folding.
syncline
Which of the following is an example of ductile deformation? Choose all that apply
syncline anticline dome
Which kind of fold is visible in figure 3?
syncline (smile-shaped folds also called downfolds)
Which geologic features would be present in compressional mountain belts?
thrust faults intrusive igneous rocks folds (Partial melting creates magma, which is emplaced near the plate boundary; rocks that are compressed become "wrinkled"; thrust faults result from compressional force)
Which of the following scenarios could result in the development of a compressional mountain belt?
two landmasses collide (when two landmasses collide, such as a convergent plate boundary, the edges will fold and buckle to create mountains)
Batholiths, such as those that make up the Sierra Nevada Mountains of California, form at great depth in the crust. How could they have been exposed at the surface?
uplift and erosion (the batholiths would have been uplifted as the continent rose and exposed through erosion)
Which event marked the creation of the supercontinent Pangaea?
Iapetus Ocean closed during Alleghanian Orogeny (The AO was last of 3 orogenies that created the Appalachians when Pangaea formed)
Drag labels to respective targets
Top L = anticline Top R = syncline Bottom R = axial plane Bottom L = shared limb
Using the map in Figure 1, determine which of the named terranes accreted earliest to North America.
Yukon-Tanana (The Yukon-Tanana Terrane was accreted sometime during the Paleozoic Era)
A horst is ________.
an uplifted fault bounded by two normal faults
If a rock undergoes folding and is compressed to form an upward arch, this is a(n) _____ type fold
anticline
which type of fold has rocks folding up the middle?
anticline (also known as upfolds)
Based on the ages of the rock layers in the cross-section, what kind of fold is in Figure 1? (Note: In map view, this feature would have a bull's-eye pattern)
basin (basins have the youngest rocks in the center and the oldest on the outside)
Identify the type of deformation the rock has been exposed to. Drag appropriate labels.
brittle ductile elastic
What scenario best describes the deformation that will occur in different parts of the crust?
brittle deformation is dominant in the shallow crust; ductile deformation is dominant in the deep crust (temps are low near the surface, making the rock "cold" and more likely to shatter)
What kind of force would create the fault in Figure 1?
compression (compressional force creates reverse and thrust faults)
Which type of force causes folding?
compressional force
convergent plate boundary
compressional stress
what type of stress can cause folding (only type)
compressional stress
Which type of plate boundary is most associated with Earth's major mountain chains?
convergent plate boundary
what plate tectonic boundary will contain folded rocks?
convergent plate boundary
Match the type of stress you'd expect to find w/ the appropriate plate tectonic boundary
convergent plate boundary: divergent plate boundary: transform plate boundary:
using what you know about isostasy, how would the crust behave if a large glacier were removed?
crust would move up in elevation (crust will bounce back after glaciation just like it would if large mountains would erode)
If strike and dips symbols were placed on a map of a basin, which way would the dips point?
dips point down toward the center (basins are similar in shape to a bowl, where the lowest point is in the center)
What kind of structure is present in Figure 2?
dome (domes are round structures that arch upward)
What type of deformation is shown in the Gigapan image?
ductile
What two strains causes permanent deformation?
ductile (plastic) brittle
a geologic map is
graphic representation of geological architecture both above and below ground
Which process can decrease the height of a mountain?
gravitational collapse
